Influenza has a long history of pandemics, epidemics, resurgences and outbreaks. Among influenza strains, H2 strains pose particular challenges in light of the waning population immunity to H2 hemagglutinin. There is a need for vaccines and therapeutic strategies for effective treatment or delay of onset of disease caused by influenza virus; there is a particular need for vaccines and therapeutic strategies for effective treatment or delay of onset of disease caused by H2 influenza viruses.